Process for discharging impurities from a hydrocyclone and a hydrocyclone

ABSTRACT

A hydrocyclone and a process for discharging impurities from a suspension containing paper fibers using a hydrocyclone having a radially inner area. The hydrocyclone includes an inflow for introducing the suspension to be purified, an accepted stock outflow for discharging the purified suspension, a separating part, a reject discharge device for discharging impurities of the suspension, at least one element for adding a diluting liquid at an addition point which is located in a radially inner area of the hydrocyclone, wherein the at least one element has at least one aperture opening axially and opposite to a discharge direction of the impurities. The process includes adding a diluting liquid into the suspension in the radially inner area of the hydrocyclone, wherein the diluting liquid is added in a flow direction opposite to an axial discharge direction of the impurities.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of GermanPatent Application No. 199 31 166.8, filed on Jul. 6, 1999 and GermanPatent Application No. 200 04 255.6, filed on Mar. 7, 2000, thedisclosure of which is expressly incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process for discharging impurities from asuspension containing paper fibers using a hydrocyclone in whichdiluting liquid is added into the suspension in the radially inner areaof the hydrocyclone. The invention also relates to a hydrocyclone forcarrying out the process.

2. Discussion of Background Information

As is known, hydrocyclones are well suited to concentrating the heavyparts and/or the light parts of a pulp suspension. Such devicestypically utilize centrifugal forces in order to conduct such parts outof the hydrocyclone through a discharge aperture provided for thispurpose. As a rule, hydrocyclones also serve to remove impurities suchas small metal parts, glass slivers, sand, styropor, as well as lightplastics. Moreover, it is important for such devices to achieve a highseparating effect with increased operational reliability, e.g., freedomfrom clogging. In these known devices, clogs can occur when theimpurities collect together and become concentrated in specificlocations, e.g., in the area of the discharge aperture provided forthem. These concentrations can accumulate over time in such a way thatthey result in a blockage. In many cases, a compromise must be foundbetween the operational reliability of the device, e.g., the avoidanceof clogs, and the highest possible efficiency of the machine, e.g.,throughput and/or separating effect. One known method which attempts toaddress the problem of clogging utilizes the feeding in a dilutingliquid in heavy-part hydrocyclones. Such a device utilizes a water feedline which opens in an edge area of the hydrocyclone, e.g., throughslits in the cyclone wall in the peripheral direction. The dilutingliquid acts to cause eddies at the edge layers. However, this designsuffers from the fact that the diluted liquid must penetrate the heavysoil that is already concentrated therein, which can lead to a backwashing of heavy parts into the accepted stock stream.

Other solutions utilize a central pipe having apertures facing radiallyoutwards for adding the diluting liquid. For example, Canadian PatentApplication No. 1 138 378 A describes a device wherein the dilutingliquid quickly reaches the wall of the hydrocyclone with the detrimentaleffects already described. In such a design, undesired rebound effectscan arise owing to the short distance and the flow of the dilutingliquid directly onto the cyclone wall. Moreover, there is also anincreased risk of clogging of the apertures, which are kept relativelysmall. In addition, the suggested swirl flow leads to furtherinterfering eddies.

A known design is described in U.S. Pat. No. 3,785,489. This deviceutilizes an axial outflow. However, the design also produces a rotatingflow at the central inflow of the diluting water by way of a number ofvanes. Accordingly, this flow quickly drives the diluting wateroutwards. The effect of this flow is also an increased risk of clogging.

SUMMARY OF THE INVENTION

The invention is therefore directed to a process for dischargingimpurities from hydrocyclones which enables both an operationally morereliable removal of the impurities and a good separating effect.

According to the invention, the diluting liquid is introducedapproximately centrally and in an axial direction rather than at theedge of the hydrocyclone, where clogging can be expected. Moreover, thisdesign provides for the introduction of the diluting fluid predominantlyinto the core flow. Accordingly, if the rate of inflow is sufficientlyhigh, the diluting liquid reaches the conical area of the separatingchamber and gradually mixes with the surrounding pulp suspension owingto the effect of the shear flow prevailing there. This type of dilutionleads to a gentle backwash of the fibers into the accepted stock, butwithout this happening to already concentrated heavy parts as well. Thereason being that the latter are at the wall and are not affected by theaddition of the diluting water. Without the measures of the invention, aportion of the already concentrated heavy parts could be stirred up andmight reach the center of the hydrocyclone. From there, they would thendisadvantageously be discharged with the accepted stock.

The invention provides for a process for discharging impurities from asuspension containing paper fibers using a hydrocyclone comprising aradially inner area, the process comprising adding a diluting liquidinto the suspension in the radially inner area of the hydrocyclone,wherein the diluting liquid is added in a flow direction opposite to anaxial discharge direction of the impurities. The hydrocyclone maycomprise a separating cone having a narrowest point and an additionpoint wherein the diluting liquid is added. The addition point may beaxially displaced from the narrowest point by a distance “a”. Thedistance “a” may comprise an axial length which is no greater thanapproximately 30% of an axial length of the hydrocyclone. The adding maycomprise adding a flow of the diluting liquid without swirl. The addingmay comprise adding a flow of the diluting liquid with only a swirlwhose resulting flow rate vector is defined by a peripheral speed (Vu)and axial speed (Vax) at an edge of a jet, the resulting flow ratevector having an angle (α) relative to an axial axis of no greater thanapproximately 30°. The adding may comprise adding the diluting liquidvia a smooth jet. The adding may comprise adding the diluting liquid viaa round jet. The adding may comprise adding the diluting liquid via aring-shaped jet. The adding may comprise adding the diluting liquid intoa center portion of the radially inner area with the aid of an injector,the injector drawing in liquid from a ring-shaped area around anaddition point. The adding may comprise adding the diluting liquid at anaxial speed of at least approximately 4 m/s.

The process may further comprise forming a light fraction from thesuspension containing paper fibers, the light fraction comprising anaccepted stock. The process may further comprise separating out a heavyfraction from the suspension, the heavy fraction comprising heavy parts.

The invention also provides for a hydrocyclone for dischargingimpurities from a suspension containing paper fibers, the hydrocyclonecomprising an inflow for introducing the suspension to be purified, anaccepted stock outflow for discharging the purified suspension, aseparating part, a reject discharge device for discharging impurities ofthe suspension, at least one element for adding a diluting liquid at anaddition point which is located in a radially inner area of thehydrocyclone, wherein the at least one element has at least one apertureopening axially and opposite to a discharge direction of the impurities.The reject discharge device may be directly attached to the separatingpart. The reject discharge device may be indirectly attached to theseparating part. The addition point may be located away from the inflowat a point which is at least approximately 70% of an axial length of thehydrocyclone. The the separating part may comprise a separating cone.The addition point may be disposed on part of a flow insert which islocated inside the hydrocyclone. The flow insert may be removable. Thehydrocyclone may be adapted to accept different flow inserts havingdifferent flow actions. The at least one aperture may comprise anadjustable cross section. The position of the at least one aperture maybe adjustable. The addition point may be arranged to be concentric withrespect to a center of the hydrocyclone. The addition point may bearranged to be eccentric with respect to a center of the hydrocyclone.The addition point may be located at a distance from an inside wall ofthe hydrocyclone, the distance being at least approximately 10% of anadjacent inside diameter of the hydrocyclone. The addition point maycomprise a mouth end of an inflow pipe which is introduced into thehydrocyclone at a position which is below a narrowest cross sectionportion of the separating part.

Other exemplary embodiments and advantages of the present invention maybe ascertained by reviewing the present disclosure and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed descriptionwhich follows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention,in which like reference numerals represent similar parts throughout theseveral views of the drawings, and wherein:

FIG. 1 shows the process being carried out based on a heavy parthydrocyclone in side view, in section;

FIGS. 2-4 show variants for the addition of the diluting liquid;

FIG. 5 shows a vector diagram of specific speeds at the edge of the jetof the diluting liquid;

FIG. 6 shows a perspective view of a hydrocyclone according to theinvention; and

FIGS. 7-8 each show another variant of the lower part of thehydrocyclone according to the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present invention onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show structural details of the present invention in moredetail than is necessary for the fundamental understanding of thepresent invention, the description taken with the drawings makingapparent to those skilled in the art how the several forms of thepresent invention may be embodied in practice.

FIG. 1 shows a rough schematic of a hydrocyclone according to theinvention. The hydrocyclone utilizes an inflow 2 for introducing asuspension S containing paper fibers and an accepted stock outflow 3 fordischarging a purified suspension, i.e., an accepted stock A. SuspensionS, which is to be purified, is subjected to rotation and eventuallyreaches separating part 6. Separating part 6 utilizes a separating cone1, in which as a rule, the speed of rotation is again increased. Thisdesign causes the contained heavy parts ST to be concentrated at theinside wall of separating cone 1 so that they travel downwards along thewall into a reject discharge device 17.

According to the invention, a diluting liquid W is introduced into aradially inner area of the hydrocyclone via an axial direction. Here, anaddition point 5 is located at a distance “a” from a narrowest point 4of separating cone 1. Distance “a” is preferably approximately a fewmillimeters at most. In some specific embodiments, distance “a” can beup to approximately 30% of the length L of the hydrocyclone. Anotherembodiment may require that the axial distance from inflow 2 be kept aslong as possible, e.g., at least approximately 70% of the length L ofthe hydrocyclone.

After heavy parts ST have passed narrowest point 4 of separating cone 1,they fall into a discharge chamber 8, from which they are removed asrejects R, e.g., via discharge device 17. Accordingly, it should benoted that this discharging can be performed continuously or in anintermittent manner.

In the example shown here, diluting liquid W is added through a simplevertical inflow pipe 9, which at addition point 5 has an aperture whichopens axially and opposite to the discharge direction of heavy parts orimpurities ST. This figure also shows schematically that added liquid Wpredominantly reaches the central core flow of the hydrocyclone.Moreover, it is important that the falling impurities ST can fall intodischarge chamber 8 in as undisturbed manner as possible, e.g., withoutbeing subjected to eddies, etc. On the other hand, the addition ofliquid W enables an undesired concentration of the heavy fraction to becompletely prevented, since a partial dilution is also possible in theouter areas of separating cone 1. However, the diluting effect and theassociated cross flows produced by this design, e.g., eddies, etc.,weaken successively towards the cone wall, so that an impairment of theseparating effect does not become significant. These processes areindicated by the broken arrows 10. Moreover, if, in specific cases, aslight rotation of the exiting diluting water stream cannot be avoided,its peripheral component Vu (see FIG. 5) would need to be kept so low incomparison with an axial speed Vax, that the angle α between theresultant of the two vectors and the axis is not greater than 30°.Overall, utilizing this method of adding the diluting water, the mixingis distributed over a considerably larger volume and is thus lessdetrimental to the separating effect.

The invention advantageously provides for Liquid W to be introduced intothe hydrocyclone at a certain axial position. Accordingly, only oneaperture need be present at addition point 5. Moreover, if necessary,the position of addition point 5 can be adjusted in the axial direction.Accordingly, this position and/or adjustment can be determinedempirically or made to be continuously adjustable.

FIG. 2 shows another embodiment of a device for carrying out theprocess. In this variant, diluting liquid W is introduced via a bentinflow pipe 9′ directly into the center of an adjacent rejects pipe 11which is below separating cone 1. Here, the position, i.e., distance“a”, of addition point 5 is selected such that it lies below narrowestpoint 4. However, the position of addition point 5 may also be locatedin other locations relative to narrowest point 4, e.g., such as is shownin FIG. 1.

FIG. 3 shows another possible design for carrying out the process. Here,diluting liquid W is first fed into a flow insert 16′ in whose interiorutilizes a central displacement body 12, so that a ring-shaped flowcross section is formed. A ring-shaped jet is formed which advancesslightly into the part of separating cone 1 lying above it. The downwardpointing arrows here again show how the heavy parts ST slide downwardsin the vicinity of the wall of the hydrocyclone and into dischargechamber 8. It should be noted that this design may provide that they cando so without being washed into the core flow of the hydrocyclone by thestream of diluting liquid W.

The embodiment according to FIG. 4 shows an axial inflow of dilutingliquid W through central inflow pipe 9. Moreover, it opens into acentral pipe 14 located inside flow insert 16″ via an injector 13.According to this design, parts of the suspension can be sucked out fromthe hydrocyclone by these mechanism and be added back into the center.This design may serve to ensure a stable mode of operation and minimizesfiber loss.

FIG. 6 shows a hydrocyclone which is similar to the device shown in FIG.1 in a perspective view. Moreover, FIG. 7 essentially shows the lowerpart of FIG. 6 in enlarged form. This design utilizes inflow pipe 9which is screwed in at the precise center and opens in a circularaperture above narrowest point 4. Accordingly, this design allows forease of installation as well as adjustable axial displacement.Furthermore, utilizing this adjustable axial displacement design makesit possible to match the hydrocyclone to the conditions required.

Another embodiment of the invention is shown in FIG. 8 which utilizes adischarge chamber 8 that exhibits a slightly eccentrically locatedinflow pipe 9. However, even in this design, it remains in the radiallyinner area of the hydrocyclone. Moreover, the outflow cross section ofinflow pipe 9 maintains a distance “b” from the wall of thehydrocyclone. Accordingly, this distance may be at least approximately10% of the inside diameter of the hydrocyclone at this point so as toensure that the heavy parts that have already been concentrated are nolonger washed by the diluting liquid. The eccentricity can also provideadvantages in specific cases, e.g., such as when the hydrocyclone isoperated horizontally. Moreover, its eccentric position can also be madeadjustable.

Depending on the manner in which the flow insert 16, 16′, or 16″ isdesigned, the effects may vary when the process is carried out. Thesevarious effects may be extremely desirable as a rule. In fact, it ispossible to achieve a specific optimization of the process depending onthe application, i.e., throughput, stock density, and dirt load, tomention only a few. In practice, a considerable advantage is obtainedwhen the various flow inserts are designed so that they can beexchanged. Such as design also makes it possible to match them to theconditions without great expense, namely by simply exchanging thevariously designed flow inserts. In any case, practical maintenanceconsiderations can dictate that the flow inserts be easily removable,because it is not always possible to avoid some clogging, in spite ofall efforts to prevent them.

The flow inserts described in the figures are only intended to show theprinciple. Other flow insert designs are also contemplated. Inparticular, their dimensions and/or configurations can be matched to therespective application by calculations and/or simple testing.

It is noted that the foregoing examples have been provided merely forthe purpose of explanation and are in no way to be construed as limitingof the present invention. While the present invention has been describedwith reference to an exemplary embodiment, it is understood that thewords which have been used herein are words of description andillustration, rather than words of limitation. Changes may be made,within the purview of the appended claims, as presently stated and asamended, without departing from the scope and spirit of the presentinvention in its aspects. Although the present invention has beendescribed herein with reference to particular means, materials andembodiments, the present invention is not intended to be limited to theparticulars disclosed herein; rather, the present inventiun extends toall functionally equivalent structures, methods and uses, such as arewithin the scope of the appended claims.

What is claimed is:
 1. A process for discharging impurities from asuspension containing paper fibers using a hydrocyclone comprising aradially inner area, the process comprising: adding a diluting liquidinto the suspension in the radially inner area of the hydrocyclone,wherein the diluting liquid is added in a flow direction opposite to anaxial discharge direction of the impurities, and wherein the dilutingliquid is added via at least one aperture whose position is adjustable.2. The process of claim 1, wherein the hydrocyclone comprises aseparating cone having a narrowest point and an addition point whereinthe diluting liquid is added.
 3. The process of claim 2, wherein theaddition point is axially displaced from the narrowest point by adistance “a”.
 4. The process of claim 3, wherein the distance “a”comprises an axial length which is no greater than approximately 30% ofan axial length of the hydrocyclone.
 5. The process of claim 1, whereinthe adding comprises adding a flow of the diluting liquid without swirl.6. The process of claim 1, wherein the adding comprises adding a flow ofthe diluting liquid with only a swirl whose resulting flow rate vectoris defined by a peripheral speed (Vu) and axial speed (Vax) at an edgeof a jet, the resulting flow rate vector having an angle (α) relative toan axial axis of no greater than approximately 30°.
 7. The process ofclaim 1, wherein the adding comprises adding the diluting liquid via asmooth jet.
 8. The process of claim 1, wherein the adding comprisesadding the diluting liquid via a round jet.
 9. The process of claim 1,wherein the adding comprises adding the diluting liquid via aring-shaped jet.
 10. The process of claim 1, wherein the addingcomprises adding the diluting liquid into a center portion of theradially inner area with the aid of an injector, the injector drawing inliquid from a ring-shaped area around an addition point.
 11. The processof claim 1, wherein the adding comprises adding the diluting liquid atan axial speed of at least approximately 4 m/s.
 12. The process of claim1, further comprising forming a light fraction from the suspensioncontaining paper fibers, the light fraction comprising an acceptedstock.
 13. The process of claim 12, further comprising separating out aheavy fraction from the suspension, the heavy fraction comprising heavyparts.
 14. A process for discharging impurities from a suspensioncontaining paper fibers using a hydrocyclone comprising a radially innerarea, the process comprising: adding a diluting liquid into thesuspension in the radially inner area of the hydrocyclone, the dilutingliquid being added in a flow direction opposite to an axial dischargedirection of the impurities, wherein the adding comprises adding a flowof the diluting liquid with only a swirl whose resulting flow ratevector is defined by a peripheral speed (Vu) and axial speed (Vax) at anedge of a jet, the resulting flow rate vector having an angle (α)relative to an axial axis of no greater than approximately 30°.
 15. Aprocess for discharging impurities from a suspension containing paperfibers using a hydrocyclone comprising a radially inner area, theprocess comprising: adding a diluting liquid into the suspension in theradially inner area of the hydrocyclone, the diluting liquid being addedin a flow direction opposite to an axial discharge direction of theimpurities, wherein the adding comprises adding the diluting liquid viaa ring-shaped jet.
 16. A process for discharging impurities from asuspension containing paper fibers using a hydrocyclone comprising aradially inner area, the process comprising: adding a diluting liquidinto the suspension in the radially inner area of the hydrocyclone, thediluting liquid being added in a flow direction opposite to an axialdischarge direction of the impurities, wherein the adding comprisesadding the diluting liquid into a center portion of the radially innerarea with the aid of an injector, the injector drawing in liquid from aring-shaped area around an addition point.
 17. A process for dischargingimpurities from a suspension containing paper fibers using ahydrocyclone comprising a radially inner area, the process comprising:adding a diluting liquid into the suspension in the radially inner areaof the hydrocyclone, the diluting liquid being added in a flow directionopposite to an axial discharge direction of the impurities, wherein theadding comprises adding the diluting liquid at an axial speed of atleast approximately 4 m/s.
 18. A process for discharging impurities froma suspension containing paper fibers using a hydrocyclone which includesa separating cone having a narrowest point and an addition pointdisposed in an area of the narrowest point, the process comprising:adding the diluting liquid into the suspension via the addition point,wherein the diluting liquid is added without swirl in a flow directionopposite to an axial discharge direction of the impurities.
 19. Aprocess for discharging impurities from a suspension containing paperfibers using a hydrocyclone which includes a separating cone having anarrowest point and an addition point disposed within the separatingcone, the process comprising: adding the diluting liquid into thesuspension via the addition point, wherein the diluting liquid is addedwithout swirl in a flow direction opposite to an axial dischargedirection of the impurities.
 20. A process for discharging impuritiesfrom a suspension containing paper fibers using a hydrocyclone whichincludes a separating cone having a narrowest point and an additionpoint adjustably positioned in the separation cone, the processcomprising: adding the diluting liquid into the suspension via theaddition point, wherein the diluting liquid is added without swirl in aflow direction opposite to an axial discharge direction of theimpurities.
 21. A hydrocyclone for discharging impurities from asuspension containing paper fibers, the hydrocyclone comprising: aninflow for introducing the suspension to be purified; an accepted stockoutflow for discharging the purified suspension; a separating part; areject discharge device for discharging impurities of the suspension; atleast one element for adding a diluting liquid at an addition pointwhich is located in a radially inner area of the hydrocyclone, the atleast one element having at least one aperture opening axially andopposite to a discharge direction of the impurities, wherein theposition of the at least one aperture is adjustable.
 22. Thehydrocyclone of claim 21, wherein the reject discharge device isdirectly attached to the separating part.
 23. The hydrocyclone of claim21, wherein the reject discharge device is indirectly attached to theseparating part.
 24. The hydrocyclone of claim 21, wherein the additionpoint is located away from the inflow at a point which is at leastapproximately 70% of an axial length of the hydrocyclone.
 25. Thehydrocyclone of claim 24, wherein the separating part comprises aseparating cone.
 26. The hydrocyclone of claim 21, wherein the additionpoint is disposed on part of a flow insert which is located inside thehydrocyclone.
 27. The hydrocyclone of claim 26, wherein the flow insertis removable.
 28. The hydrocyclone of claim 27, wherein the hydrocycloneis adapted to accept different flow inserts having different flowactions.
 29. The hydrocyclone of claim 21, wherein the at least oneaperture comprises an adjustable cross section.
 30. The hydrocyclone ofclaim 21, wherein the addition point is arranged to be concentric withrespect to a center of the hydrocyclone.
 31. The hydrocyclone of claim21, wherein the addition point is arranged to be eccentric with respectto a center of the hydrocyclone.
 32. The hydrocyclone of claim 31,wherein the addition point is located at a distance from an inside wallof the hydrocyclone, the distance being at least approximately 10% of anadjacent inside diameter of the hydrocyclone.
 33. The hydrocyclone ofclaim 21, wherein the addition point comprises a mouth end of an inflowpipe which is introduced into the hydrocyclone at a position which isbelow a narrowest cross section portion of the separating part.
 34. Ahydrocyclone for discharging impurities from a suspension containingpaper fibers, the hydrocyclone comprising: an inflow for introducing thesuspension to be purified; an accepted stock outflow for discharging thepurified suspension; a separating part; a reject discharge device fordischarging impurities of the suspension; at least one element foradding a diluting liquid at an addition point which is located in aradially inner area of the hydrocyclone, the at least one element havingat least one aperture opening axially and opposite to a dischargedirection of the impurities, wherein the addition point is disposed onpart of a flow insert which is located inside the hydrocyclone.
 35. Thehydrocyclone of claim 34, wherein the flow insert is removable.
 36. Thehydrocyclone of claim 35, wherein the hydrocyclone is adapted to acceptdifferent flow inserts having different flow actions.
 37. A hydrocyclonefor discharging impurities from a suspension containing paper fibers,the hydrocyclone comprising: an inflow for introducing the suspension tobe purified; an accepted stock outflow for discharging the purifiedsuspension; a separating part; a reject discharge device for dischargingimpurities of the suspension; at least one element for adding a dilutingliquid at an addition point which is located in a radially inner area ofthe hydrocyclone, the at least one element having at least one apertureopening axially and opposite to a discharge direction of the impurities,wherein the at least one aperture comprises an adjustable cross section.38. A hydrocyclone for discharging impurities from a suspensioncontaining paper fibers, the hydrocyclone comprising: an inflow forintroducing the suspension to be purified; an accepted stock outflow fordischarging the purified suspension; a separating part; a rejectdischarge device for discharging impurities of the suspension; at leastone element for adding a diluting liquid at an addition point which islocated in a radially inner area of the hydrocyclone, the at least oneelement having at least one aperture opening axially and opposite to adischarge direction of the impurities, wherein the addition point isarranged to be eccentric with respect to a center of the hydrocyclone.39. The hydrocyclone of claim 38, wherein the addition point is locatedat a distance from an inside wall of the hydrocyclone, the distancebeing at least approximately 10% of an adjacent inside diameter of thehydrocyclone.
 40. A hydrocyclone for discharging impurities from asuspension containing paper fibers, the hydrocyclone comprising: aninflow for introducing the suspension to be purified; an accepted stockoutflow for discharging the purified suspension; a separating part; areject discharge device for discharging impurities of the suspension; atleast one element for adding a diluting liquid at an addition pointwhich is located in a radially inner area of the hydrocyclone, the atleast one element having at least one aperture opening axially andopposite to a discharge direction of the impurities, wherein the atleast one aperture is adapted to add a flow of the diluting liquidwithout swirl.